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Park SD, Saunders AS, Reidy MA, Bender DE, Clifton S, Morris KT. A review of granulocyte colony-stimulating factor receptor signaling and regulation with implications for cancer. Front Oncol 2022; 12:932608. [PMID: 36033452 PMCID: PMC9402976 DOI: 10.3389/fonc.2022.932608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 07/15/2022] [Indexed: 12/29/2022] Open
Abstract
Granulocyte colony-stimulating factor receptor (GCSFR) is a critical regulator of granulopoiesis. Studies have shown significant upregulation of GCSFR in a variety of cancers and cell types and have recognized GCSFR as a cytokine receptor capable of influencing both myeloid and non-myeloid immune cells, supporting pro-tumoral actions. This systematic review aims to summarize the available literature examining the mechanisms that control GCSFR signaling, regulation, and surface expression with emphasis on how these mechanisms may be dysregulated in cancer. Experiments with different cancer cell lines from breast cancer, bladder cancer, glioma, and neuroblastoma are used to review the biological function and underlying mechanisms of increased GCSFR expression with emphasis on actions related to tumor proliferation, migration, and metastasis, primarily acting through the JAK/STAT pathway. Evidence is also presented that demonstrates a differential physiological response to aberrant GCSFR signal transduction in different organs. The lifecycle of the receptor is also reviewed to support future work defining how this signaling axis becomes dysregulated in malignancies.
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Affiliation(s)
- Sungjin David Park
- Department of Surgery, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Apryl S. Saunders
- Department of Surgery, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Megan A. Reidy
- Department of Surgery, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Dawn E. Bender
- Department of Surgery, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Shari Clifton
- Department of Information Management, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Katherine T. Morris
- Department of Surgery, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
- *Correspondence: Katherine T. Morris,
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T618I CSF3R mutations in chronic neutrophilic leukemia induce oncogenic signals through aberrant trafficking and constitutive phosphorylation of the O-glycosylated receptor form. Biochem Biophys Res Commun 2019; 523:208-213. [PMID: 31848046 DOI: 10.1016/j.bbrc.2019.12.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 12/05/2019] [Indexed: 12/19/2022]
Abstract
Activating mutations in the membrane-proximal region of the colony-stimulating factor 3 receptor (CSF3R) are a hallmark of chronic neutrophilic leukemia (CNL) with the T618I mutation being most common. The mechanisms underlying constitutive activation of the T618I CSF3R and its signal propagation are poorly understood. Ligand-independent activation of the T618I CSF3R has previously been attributed to loss of receptor O-glycosylation and increased receptor dimerization. Here, we show that the T618I CSF3R is indeed glycosylated but undergoes enhanced spontaneous internalization and degradation that results in a marked decrease in its surface expression. Inhibition of the proteasome dramatically increases expression of the O-glycosylated T618I CSF3R. We also demonstrate that the O-glycosylated wild-type CSF3R is tyrosine phosphorylated in response to ligand but constitutively phosphorylated in cells expressing T618I CSF3R. Constitutive tyrosine phosphorylation of the O-glycosylated T618I receptor form correlated with activation of JAK2 and both the mutant receptor and JAK2 were found to be constitutively ubiquitinated. These observations provide novel insights into the mechanisms of oncogenic signaling by T618I CSF3R mutations in CNL.
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3
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De Alessandris S, Ferguson GJ, Dodd AJ, Juss JK, Devaprasad A, Piper S, Wyatt O, Killick H, Corkill DJ, Cohen ES, Pandit A, Radstake TRDJ, Simmonds R, Condliffe AM, Sleeman MA, Cowburn AS, Finch DK, Chilvers ER. Neutrophil GM-CSF receptor dynamics in acute lung injury. J Leukoc Biol 2019; 105:1183-1194. [PMID: 30942918 PMCID: PMC6850700 DOI: 10.1002/jlb.3ma0918-347r] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/18/2019] [Accepted: 03/12/2019] [Indexed: 11/13/2022] Open
Abstract
GM‐CSF is important in regulating acute, persistent neutrophilic inflammation in certain settings, including lung injury. Ligand binding induces rapid internalization of the GM‐CSF receptor (GM‐CSFRα) complex, a process essential for signaling. Whereas GM‐CSF controls many aspects of neutrophil biology, regulation of GM‐CSFRα expression is poorly understood, particularly the role of GM‐CSFRα in ligand clearance and whether signaling is sustained despite major down‐regulation of GM‐CSFRα surface expression. We established a quantitative assay of GM‐CSFRα surface expression and used this, together with selective anti‐GM‐CSFR antibodies, to define GM‐CSFRα kinetics in human neutrophils, and in murine blood and alveolar neutrophils in a lung injury model. Despite rapid sustained ligand‐induced GM‐CSFRα loss from the neutrophil surface, which persisted even following ligand removal, pro‐survival effects of GM‐CSF required ongoing ligand‐receptor interaction. Neutrophils recruited to the lungs following LPS challenge showed initially high mGM‐CSFRα expression, which along with mGM‐CSFRβ declined over 24 hr; this was associated with a transient increase in bronchoalveolar lavage fluid (BALF) mGM‐CSF concentration. Treating mice in an LPS challenge model with CAM‐3003, an anti‐mGM‐CSFRα mAb, inhibited inflammatory cell influx into the lung and maintained the level of BALF mGM‐CSF. Consistent with neutrophil consumption of GM‐CSF, human neutrophils depleted exogenous GM‐CSF, independent of protease activity. These data show that loss of membrane GM‐CSFRα following GM‐CSF exposure does not preclude sustained GM‐CSF/GM‐CSFRα signaling and that this receptor plays a key role in ligand clearance. Hence neutrophilic activation via GM‐CSFR may play an important role in neutrophilic lung inflammation even in the absence of high GM‐CSF levels or GM‐CSFRα expression.
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Affiliation(s)
| | - G John Ferguson
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Alison J Dodd
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Jatinder K Juss
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Abhinandan Devaprasad
- Department of Rheumatology and Clinical Immunology and Laboratory of Translational Immunology, University Medical Centre, Utrecht, Netherlands
| | - Siân Piper
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Owen Wyatt
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Helen Killick
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Dominic J Corkill
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - E Suzanne Cohen
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Aridaman Pandit
- Department of Rheumatology and Clinical Immunology and Laboratory of Translational Immunology, University Medical Centre, Utrecht, Netherlands
| | - Timothy R D J Radstake
- Department of Rheumatology and Clinical Immunology and Laboratory of Translational Immunology, University Medical Centre, Utrecht, Netherlands
| | - Rosalind Simmonds
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Alison M Condliffe
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Matthew A Sleeman
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Andrew S Cowburn
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Donna K Finch
- Respiratory, Inflammation and Autoimmunity, MedImmune Ltd., Cambridge, United Kingdom
| | - Edwin R Chilvers
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
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Genome-wide common and rare variant analysis provides novel insights into clozapine-associated neutropenia. Mol Psychiatry 2017; 22:1502-1508. [PMID: 27400856 PMCID: PMC5065090 DOI: 10.1038/mp.2016.97] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/10/2016] [Accepted: 05/17/2016] [Indexed: 01/31/2023]
Abstract
The antipsychotic clozapine is uniquely effective in the management of schizophrenia; however, its use is limited by its potential to induce agranulocytosis. The causes of this, and of its precursor neutropenia, are largely unknown, although genetic factors have an important role. We sought risk alleles for clozapine-associated neutropenia in a sample of 66 cases and 5583 clozapine-treated controls, through a genome-wide association study (GWAS), imputed human leukocyte antigen (HLA) alleles, exome array and copy-number variation (CNV) analyses. We then combined associated variants in a meta-analysis with data from the Clozapine-Induced Agranulocytosis Consortium (up to 163 cases and 7970 controls). In the largest combined sample to date, we identified a novel association with rs149104283 (odds ratio (OR)=4.32, P=1.79 × 10-8), intronic to transcripts of SLCO1B3 and SLCO1B7, members of a family of hepatic transporter genes previously implicated in adverse drug reactions including simvastatin-induced myopathy and docetaxel-induced neutropenia. Exome array analysis identified gene-wide associations of uncommon non-synonymous variants within UBAP2 and STARD9. We additionally provide independent replication of a previously identified variant in HLA-DQB1 (OR=15.6, P=0.015, positive predictive value=35.1%). These results implicate biological pathways through which clozapine may act to cause this serious adverse effect.
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Abstract
FBW7 (F-box and WD repeat domain-containing 7) or Fbxw7 is a tumor suppressor, which promotes the ubiquitination and subsequent degradation of numerous oncoproteins including Mcl-1, Cyclin E, Notch, c- Jun, and c-Myc. In turn, FBW7 is regulated by multiple upstream factors including p53, C/EBP-δ, EBP2, Pin1, Hes-5 and Numb4 as well as by microRNAs such as miR-223, miR-27a, miR-25, and miR-129-5p. Given that the Fbw7 tumor suppressor is frequently inactivated or deleted in various human cancers, targeting FBW7 regulators is a promising anti-cancer therapeutic strategy.
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Wright CR, Brown EL, Della-Gatta PA, Ward AC, Lynch GS, Russell AP. G-CSF does not influence C2C12 myogenesis despite receptor expression in healthy and dystrophic skeletal muscle. Front Physiol 2014; 5:170. [PMID: 24822049 PMCID: PMC4013466 DOI: 10.3389/fphys.2014.00170] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 04/11/2014] [Indexed: 02/01/2023] Open
Abstract
Granulocyte-colony stimulating factor (G-CSF) increases recovery of rodent skeletal muscles after injury, and increases muscle function in rodent models of neuromuscular disease. However, the mechanisms by which G-CSF mediates these effects are poorly understood. G-CSF acts by binding to the membrane spanning G-CSFR and activating multiple intracellular signaling pathways. Expression of the G-CSFR within the haematopoietic system is well known, but more recently it has been demonstrated to be expressed in other tissues. However, comprehensive characterization of G-CSFR expression in healthy and diseased skeletal muscle, imperative before implementing G-CSF as a therapeutic agent for skeletal muscle conditions, has been lacking. Here we show that the G-CSFR is expressed in proliferating C2C12 myoblasts, differentiated C2C12 myotubes, human primary skeletal muscle cell cultures and in mouse and human skeletal muscle. In mdx mice, a model of human Duchenne muscular dystrophy (DMD), G-CSF mRNA and protein was down-regulated in limb and diaphragm muscle, but circulating G-CSF ligand levels were elevated. G-CSFR mRNA in the muscles of mdx mice was up-regulated however steady-state levels of the protein were down-regulated. We show that G-CSF does not influence C2C12 myoblast proliferation, differentiation or phosphorylation of Akt, STAT3, and Erk1/2. Media change alone was sufficient to elicit increases in Akt, STAT3, and Erk1/2 phosphorylation in C2C12 muscle cells and suggest previous observations showing a G-CSF increase in phosphoprotein signaling be viewed with caution. These results suggest that the actions of G-CSF may require the interaction with other cytokines and growth factors in vivo, however these data provides preliminary evidence supporting the investigation of G-CSF for the management of muscular dystrophy.
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Affiliation(s)
- Craig R Wright
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Erin L Brown
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Paul A Della-Gatta
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
| | - Alister C Ward
- Molecular and Medical Research SRC, School of Medicine, Deakin University Waurn Ponds, VIC, Australia
| | - Gordon S Lynch
- Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne VIC, Australia
| | - Aaron P Russell
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University Burwood, VIC, Australia
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Chang YN, Guo H, Li J, Song Y, Zhang M, Jin J, Xing G, Zhao Y. Adjusting the balance between effective loading and vector migration of macrophage vehicles to deliver nanoparticles. PLoS One 2013; 8:e76024. [PMID: 24116086 PMCID: PMC3792996 DOI: 10.1371/journal.pone.0076024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 08/22/2013] [Indexed: 11/18/2022] Open
Abstract
The nature of macrophage allows the possibility that this cell type could be used as drug delivery system to track therapeutic drug nanoparticles (NPs) in cancer. However, there is no existing research on the regulation between effective loading of NPs and targeted delivery of macrophages. Here, we investigated the important parameters of intracellular NP quantity and the vector migration rate. Macrophage loading capacity was obtained by comparing the uptake quantity of varisized NPs, and the delivery ability of loaded cells was determined by measuring vector migration rates. We observed a positive correlation between the size of NPs and directed macrophage migration. Our findings suggest that the molecular mechanism of migration vector rate regulation involved increased expression levels of colony-stimulating factor-1 (CSF-1) receptor and integrin induced by 100-nm and 500-nm particles. The ability of macrophages uptake to varisized NPs showed the opposite trend, with the increased vector rate of cell migration influenced by NPs. We are able to demonstrate the important balance between effective macrophage loading and targeted delivery. By adjusting the balance parameters, it will be possible to utilize NPs in macrophage-mediated disease diagnosis and therapy.
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Affiliation(s)
- Ya-Nan Chang
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Haili Guo
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Juan Li
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Yan Song
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Mingyi Zhang
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Junjiang Jin
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
| | - Gengmei Xing
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
- * E-mail: (GX); (YZ)
| | - Yuliang Zhao
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Science, Beijing, China
- Chinese Academy of Science Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology of China, Beijing, China
- * E-mail: (GX); (YZ)
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Abstract
Since its discovery two decades ago, the activation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway by numerous cytokines and growth factors has resulted in it becoming one of the most well-studied intracellular signalling networks. The field has progressed from the identification of the individual components to high-resolution crystal structures of both JAK and STAT, and an understanding of the complexities of the molecular activation and deactivation cycle which results in a diverse, yet highly specific and regulated pattern of transcriptional responses. While there is still more to learn, we now appreciate how disruption and deregulation of this pathway can result in clinical disease and look forward to adoption of the next generation of JAK inhibitors in routine clinical treatment.
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Affiliation(s)
- Hiu Kiu
- Walter & Eliza Hall Institute, 1G Royal Parade, Parkville 3052, Australia
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Ehlers S, Herbst C, Zimmermann M, Scharn N, Germeshausen M, von Neuhoff N, Zwaan CM, Reinhardt K, Hollink IH, Klusmann JH, Lehrnbecher T, Roettgers S, Stary J, Dworzak M, Welte K, Creutzig U, Reinhardt D. Granulocyte colony-stimulating factor (G-CSF) treatment of childhood acute myeloid leukemias that overexpress the differentiation-defective G-CSF receptor isoform IV is associated with a higher incidence of relapse. J Clin Oncol 2010; 28:2591-7. [PMID: 20406937 DOI: 10.1200/jco.2009.25.9010] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE This prospective, multicenter Acute Myeloid Leukemia Berlin-Frankfurt-Muenster (AML-BFM) 98 study randomly tested the ability of granulocyte colony-stimulating factor (G-CSF) to reduce infectious complications and to improve outcomes in children and adolescents with acute myeloid leukemia (AML). However, a trend toward an increased incidence of relapses in the standard-risk (SR) group after G-CSF treatment was observed. PATIENTS AND METHODS Of 154 SR patients in the AML-BFM 98 cohort, 50 patients were tested for G-CSF receptor (G-CSFR) RNA isoform I and IV expression, G-CSFR cell surface expression, and acquired mutations in the G-CSFR gene. RESULTS In patients randomly assigned to receive G-CSF after induction, 16 patients overexpressing the G-CSFR isoform IV showed an increased 5-year cumulative incidence of relapse (50% +/- 13%) compared with 14 patients with low-level isoform IV expression (14% +/- 10%; log-rank P = .04). The level of G-CSFR isoform IV had no significant effect in patients not receiving G-CSF (P = .19). Multivariate analyses of the G-CSF-treated subgroup, including the parameters G-CSFR isoform IV overexpression, sex, and favorable cytogenetics as covariables, revealed the prognostic relevance of G-CSFR isoform IV overexpression for 5-year event-free survival (P = .031) and the 5-year cumulative incidence of relapse (P = .049). CONCLUSION Our results demonstrate that children and adolescents with AMLs that overexpress the differentiation-defective G-CSFR isoform IV respond to G-CSF administration after induction, but with a significantly higher incidence of relapse.
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Affiliation(s)
- Stephanie Ehlers
- Department of Pediatric Hematology and Oncology, Medical School Hannover, Hannover, Germany.
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Wölfler A, Irandoust M, Meenhuis A, Gits J, Roovers O, Touw IP. Site-specific ubiquitination determines lysosomal sorting and signal attenuation of the granulocyte colony-stimulating factor receptor. Traffic 2009; 10:1168-79. [PMID: 19453968 DOI: 10.1111/j.1600-0854.2009.00928.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Ubiquitination of cytokine receptors controls intracellular receptor routing and signal duration, but the underlying molecular determinants are unclear. The suppressor of cytokine signaling protein SOCS3 drives lysosomal degradation of the granulocyte colony-stimulating factor receptor (G-CSFR), depending on SOCS3-mediated ubiquitination of a specific lysine located in a conserved juxtamembrane motif. Here, we show that, despite ubiquitination of other lysines, positioning of a lysine within the membrane-proximal region is indispensable for this process. Neither reallocation of the motif nor fusion of ubiquitin to the C-terminus of the G-CSFR could drive lysosomal routing. However, within this region, the lysine could be shifted 12 amino acids toward the C-terminus without losing its function, arguing against the existence of a linear sorting motif and demonstrating that positioning of the lysine relative to the SOCS3 docking site is flexible. G-CSFR ubiquitination peaked after endocytosis, was inhibited by methyl-beta-cyclodextrin as well as hyperosmotic sucrose and severely reduced in internalization-defective G-CSFR mutants, indicating that ubiquitination mainly occurs at endosomes. Apart from elucidating structural and spatio-temporal aspects of SOCS3-mediated ubiquitination, these findings have implications for the abnormal signaling function of G-CSFR mutants found in severe congenital neutropenia, a hematopoietic disorder with a high leukemia risk.
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Affiliation(s)
- Albert Wölfler
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
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Ai J, Druhan LJ, Loveland MJ, Avalos BR. G-CSFR ubiquitination critically regulates myeloid cell survival and proliferation. PLoS One 2008; 3:e3422. [PMID: 18923646 PMCID: PMC2561048 DOI: 10.1371/journal.pone.0003422] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 09/22/2008] [Indexed: 12/22/2022] Open
Abstract
The granulocyte colony-stimulating factor receptor (G-CSFR) is a critical regulator of granulopoiesis. Mutations in the G-CSFR in patients with severe congenital neutropenia (SCN) transforming to acute myelogenous leukemia (AML) have been shown to induce hypersensitivity and enhanced growth responses to G-CSF. Recent studies have demonstrated the importance of the ubiquitin/proteasome system in the initiation of negative signaling by the G-CSFR. To further investigate the role of ubiquitination in regulating G-CSFR signaling, we generated a mutant form of the G-CSFR (K762R/G-CSFR) which abrogates the attachment of ubiquitin to the lysine residue at position 762 of the G-CSFR that is deleted in the Δ716 G-CSFR form isolated from patients with SCN/AML. In response to G-CSF, mono-/polyubiquitination of the G-CSFR was impaired in cells expressing the mutant K762R/G-CSFR compared to cells transfected with the WT G-CSFR. Cells stably transfected with the K762R/G-CSFR displayed a higher proliferation rate, increased sensitivity to G-CSF, and enhanced survival following cytokine depletion, similar to previously published data with the Δ716 G-CSFR mutant. Activation of the signaling molecules Stat5 and Akt were also increased in K762R/G-CSFR transfected cells in response to G-CSF, and their activation remained prolonged after G-CSF withdrawal. These results indicate that ubiquitination is required for regulation of G-CSFR-mediated proliferation and cell survival. Mutations that disrupt G-CSFR ubiquitination at lysine 762 induce aberrant receptor signaling and hyperproliferative responses to G-CSF, which may contribute to leukemic transformation.
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Affiliation(s)
- Jing Ai
- Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Lawrence J. Druhan
- Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Megan J. Loveland
- Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
| | - Belinda R. Avalos
- Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States of America
- Division of Hematology/Oncology, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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